Scope having focus roller

ABSTRACT

A rifle scope having a longitudinal dimension and a reticle and having an adjustment mechanism for changing the apparent reticle position seen through the scope, relative to a straight line extending along the longitudinal dimension of the scope. The scope includes an objective assembly defining an objective center line extending from the center of the assembly front to the center of the assembly back. Also, a housing includes an outer objective housing, and a tubular housing. An optical train is supported inside the tubular housing defining a train center line extending longitudinally through the center of the optical train. The objective assembly is mounted in the outer objective housing so as to have freedom to be repositioned, thereby changing the position of the assembly center line relative to the train center line and an actuation mechanism is adapted to reposition the objective assembly, in response to manipulation of the actuator.

RELATED APPLICATION

This application is a continuation of application Ser. No. 12/627,423filed Nov. 30, 2009 which claims priority from application 61/271,972,filed Jul. 29, 2009, which are incorporated by reference as if fully setforth herein.

BACKGROUND

This invention relates to variable power sighting scopes, and inparticular to a scope that provides a mechanism for reticle positionadjustment that avoids many of the problems encountered in currentlyavailable designs. A rifle scope serves to magnify the target andoverlay a visual aiming point, the reticle, on the target. It does thisthrough the use of a series of lenses mounted within a generally tubularbody and a combination of mechanisms to adjust lens positions.

The lenses in a scope can be generally divided into three groups: theobjective lens group; the erector lens group; and the ocular (oreyepiece) lens group. Depending on the particular design there may beone or more individual lenses in each group within a scope. The erectorlens group gets its name from its role in inverting the firstintermediate image, which would appear inverted (ie. upside down andflipped horizontally) to a viewer, so that the image will appear “erect”or upright to the viewer. Because of this role, any lens or otheroptical device that inverts an intermediate image will be termed anerector device or assembly in this application. The objective lens groupgathers in the light from the target and projects the target image as amagnified and inverted first intermediate image. The erector lens groupprojects the first intermediate image to a magnified or reduced, andre-inverted, second intermediate image. The ocular lens group presentsthe second image to the eye for viewing.

In a typical scope, the erector lens group is part of an erector lensassembly, which includes a guide tube that carries the erector lenses.The guide tube is mounted so that it pivots at one end, with theopposite end being adjustable horizontally and vertically to providewindage and elevation correction.

Variable magnification can be achieved by providing a means of adjustingthe position of the erector lenses in relationship to each other withinthe guide tube. This is typically done through the use of a cam tubewhich fits closely around the guide tube.

Each erector lens (or erector lens subgroup) is mounted in a lens mountwhich slides within the guide tube. A guide sleeve attached to the lensmount slides in a straight slot in the body of the guide tube tomaintain the orientation of the erector lens. This same guide sleevealso engages an angled, or curving, slot in the cam tube. Turning thecam tube causes the erector lens mount to move along a portion of thelength of the guide tube, varying the magnification. Each erector lensor lens group has its own slot in the cam tube, with the configurationof these slots determining the amount and rate of magnification changeas the cam tube is turned. Each erector lens mount has a slot followerthat fits into the corresponding cam slot.

A typical rifle scope includes a windage and an elevation knob, foradjusting the apparent position of the reticle relative to a zeroposition, which in windage is ideally the rifle bore sight, but inelevation is, ideally the rifle bore sight plus a slight down angle, tocompensate for bullet drop at some nominal range on the order of 100yards.

Another disadvantage of the windage and elevation knob design, is thetypical placement of the knobs in the center of the scope. This limitsthe placement of a hunter's scope, which is held by a set of mountingrings. It can be desirable to mount a scope fairly far forward toaccommodate eye relief (the ideal distance from the eyepiece of thescope to place one's aiming eye). The effort to mount the scope forwardon the rifle is sometimes stymied at the point where the windage knob isblocked by the front mounting ring. It would be desirable to have ascope without the structure of the windage and elevation knobs in themiddle of the scope, to permit greater freedom of scope placement, whenheld in place by mounting rings.

The windage and elevation knobs typically change the apparent reticleposition by changing the angle of the erector assembly relative to thescope housing. To maximize this affect, it is desirable to have as muchair gap between the erector assembly and the scope housing to provideroom to change the erector assembly's angular position within the scopehousing. This drives the design toward very thin-walled cam tubes. Thethin-walled cam tubes are quite delicate and can be easily bent duringthe manufacturing operation, thereby driving up the reject rate and thecosts of manufacturing. The thin-walled cam tubes also decrease theexpected useful product life, because each time the rifle is fired theslot follower is jolted violently backwards in its cam slot, potentiallydamaging the thin-walled tube. This problem is proportional to thecaliber of the rifle to which the scope is attached. For .50 caliberrifles, it tends to be impractical to provide a conventional magnifyingscope with windage and elevation adjustment due to this problem.

It is also desirable that the cam slots have a constant curvature sothat the slot follower can have length along the slot, as opposed tobeing round. Because, as noted above, rifle scopes suffer repeatedrecoil shocks, it is desirable to distribute the force from the recoilover a longer slot follower. Changes in cam slot curvature place a limiton the length of a cam slot follower. As the zoom ratio gets larger, itbecomes impossible to design a cam slot with constant curvature.Changing slot curvature can also cause a zoom actuator to be moredifficult to turn over a portion of its range. Users, however, tend toprefer that an actuator have the same “feel” over its entire range.

In known scope designs the zoom ratio is effectively limited to 4×because increasing the zoom ratio increases the range of spatialrelationships between the lenses utilized. This means that differentaspects of the lenses' shapes may be critically important at differingzoom settings. In turn, this drives tight tolerances for lens shapes andthe means of changing the spatial relationships between the lenses(discussed below), thereby increasing the defect rate, and the cost.Accordingly a need remains for a scope that can provide a zoom ratiogreater than 4× without the manufacturing, difficulty of use andlack-of-durability problems arising from the extension of known erectorlens assembly designs to provide greater zoom ratios.

Another factor limiting the zoom mechanism is the zoom actuation.Typically, a ring mounted on the scope exterior is attached directly tothe cam tube. A slot cut through the scope housing permits the ring tobe turned up to a typical maximum of about 180°. But because the directattachment, the ring cannot be turned further than length of the arc ofthe slot, which is limited by the need to preserve the structuralintegrity of the scope housing. It appears that it is known to interposea gear between a zoom actuation ring and the cam tube, however, therebyobviating the need to have a lengthy slot and permitting cam tuberotation of greater than a one-half rotation. The use of a ring as anactuator is still somewhat awkward, however, as it requires a user tomove his hand over the scope to adjust the zoom.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope. Invarious embodiments, one or more of the above-described problems havebeen reduced or eliminated, while other embodiments are directed toother improvements.

In a first separate aspect, the present invention may take the form of arifle scope having a longitudinal dimension and a reticle and having anadjustment mechanism for changing the apparent reticle position seenthrough the scope, relative to a straight line extending along thelongitudinal dimension of the scope. The scope includes an objectiveassembly having a front, through which light enters the assembly and aback, through which light leaves the assembly, and defining an objectivecenter line extending from the center of the assembly front to thecenter of the assembly back. Also, a housing includes an outer objectivehousing, and a tubular housing to the rear of the outer objectivehousing. An optical train is supported inside the tubular housing, tothe rear of the objective assembly, defining a train center lineextending longitudinally through the center of the optical train. Theobjective assembly is mounted in the outer objective housing so as tohave freedom to be repositioned, thereby changing the position of theassembly center line relative to the train center line and an actuationmechanism including an actuator is adapted to reposition the objectiveassembly, in response to user manipulation of the actuator.

In a second separate aspect, the present invention may take the form ofa rifle scope having a longitudinal extent and having windage andelevation adjust assemblies that have actuators that are positionedwithin the front 30% of the scope's longitudinal extent, therebypermitting a greater freedom of positioning when installing the scope ona rifle.

In a third separate aspect, the present invention may take the form of arifle scope that includes a housing, a zoom assembly supported insidethe housing and including a cam tube having a circumferential wall and awindage and elevation adjustment assembly, and wherein the thickness ofthe circumferential wall is greater than 0.9 mm.

In a fourth separate aspect, the present invention may take the form ofa rifle and scope assembly having a front and a back and comprising arifle, a scope mount including a front mounting ring and a rear mountingring and a scope, having a windage and elevation adjust mechanismactuation assembly and being mounted in the front mounting rings and therear mounting ring. The scope is mounted in such manner that the windageand elevation adjust mechanism actuation assembly is positioned forwardof the front mounting ring.

In a fifth separate aspect, the present invention may take the form of ascope that has a tubular housing, generally circular in cross-section anoptical train, mounted within the housing and a windage and elevationadjust actuation assembly, which changes windage and elevation angle inresponse to user adjustment of two rings mounted about the housing.

In a sixth separate aspect, the present invention may take the form of arifle scope that has a zoom mechanism having a cam tube, a windage andelevation adjust mechanism, a central tube housing having an innerdiameter and into which the cam tube is nested. Notably, the cam tube'souter diameter is within 0.5 mm of the central tube housing's innerdiameter.

In a seventh separate aspect, the present invention may take the form ofa rifle scope having windage and elevation position indicators that arereadable by a user looking through his left eye, while the user's righteye is looking through the scope's eyepiece.

In an eighth separate aspect, the present invention may take the form ofa rifle scope having a rotatable elevation adjust actuator that may beturned through no more than a single rotation.

In a ninth separate aspect, the present invention may take the form of arifle scope having an outer objective housing and a separate objectiveassembly housing that fits into the outer objective housing, and whereinthe outer objective housing defines a rearward facing ball seat ring andthe objective assembly housing has a front surface shaped to fitconformally into the ball seat ring.

In a tenth separate aspect, the present invention may take the form of ascope having an erector tube and an elevation adjust assembly that doesnot cause a change in orientation of the erector tube.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced drawings. It isintended that the embodiments and figures disclosed herein are to beconsidered illustrative rather than restrictive.

FIG. 1 is a perspective view of a rifle scope according to the presentinvention.

FIG. 2 is a side view of the scope of FIG. 1.

FIG. 3 is a side sectional view of the scope of FIG. 1.

FIG. 4 is a schematic ray trace diagram showing a prior art scopeutilizing a single 4× zoom erector assembly and in which the lenses arearranged so that the scope magnifies by 3×.

FIG. 5 is a schematic ray trace diagram showing a prior art scopeutilizing a single 4× zoom erector assembly and in which the lenses arearranged so that the scope magnifies by 12×.

FIG. 6 is ray trace diagram showing a first embodiment of the inventionincorporating three erector lens assemblies and in which the lenses arearranged so that the zoom mechanism does not magnify the image.

FIG. 7 is ray trace diagram showing a first embodiment of the inventionincorporating three erector lens assemblies and in which the lenses arearranged so that the zoom mechanism magnify the image by 15×.

FIG. 8 is a ray trace diagram showing a second embodiment of a riflescope according to the present invention, which incorporates two erectorlens assemblies in combination with a roof prism erector, configured toprovide 15× magnification.

FIG. 9 is a ray trace diagram of the rifle scope of FIG. 6, configuredto provide 10× magnification.

FIG. 10 is a ray trace diagram of the rifle scope of FIG. 6, configuredto provide 5× magnification.

FIG. 11 is a ray trace diagram of the rifle scope of FIG. 6, configuredto provide 1.5× magnification.

FIG. 12A is a perspective view of the cam tube and a set of lenses andlens mounts, removed from the cam tube for ease of presentation butmaintained in orientation, used in the erector assembly of the riflescope according to the present invention.

FIG. 12B is a perspective sectional view of the cam tube and a set oflenses and lens mounts used in the erector assembly of the rifle scopeof FIG. 12A.

FIG. 13A is a detail of the objective assembly of the scope of FIG. 1.

FIG. 13B is a perspective exploded view of the assembly of FIG. 13A.

FIG. 13C is a detail, expanded view of the windage drive ring of theassembly of FIG. 13A.

FIG. 14 is an exploded perspective view of the scope of FIG. 1 showingthe zoom actuator assembly and the focus actuator assembly.

FIG. 15 is a perspective view of the rifle scope of FIG. 1, showing thezoom actuator and focus actuator engaged with the zoom mechanism andfocus mechanism, respectively, and with the central housing removed, forgreater clarity of presentation.

FIG. 16A is an exploded view of the focus mechanism of the scope of FIG.1.

FIG. 16B is a perspective sectional view of the focus mechanism of FIG.16A.

FIG. 17 is a side view of a scope, according to the present invention,mounted on a rifle.

FIG. 18, is a side sectional view of an alternative zoom actuationmechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1, 2 and 3, a scope 10 according to a preferredembodiment of the present invention includes a body or housing 12, whichincludes an objective assembly outer housing 14, an ocular assemblyhousing 16, a central tube housing 17 and a reticle 19. In addition awindage adjust assembly 18, an elevation adjust assembly 20 and a zoomactuator assembly 22 permit a range of adjustments.

Referring now to FIGS. 4 and 5, a typical prior art 4× zoom opticalscope 110 is illustrated schematically in a ray trace diagram. Scope 110includes objective lens assembly 112, ocular lens assembly 114, and asingle 4× zoom erector lens assembly 116. A first intermediate image 118is inverted relative to the target, and a second intermediate image 120is re-inverted, to appear correctly oriented to a viewer looking throughocular lens assembly 114. In FIG. 4 the erector lens assembly 116 isconfigured to provide a magnification of 1×, whereas in FIG. 5 it isconfigured to provide a magnification of 4×.

For a scope having a length of less than 20 cm a zoom ratio of about 4×to 6× represents the practical limit of a single erector assembly scopegiven the design and manufacturing complexities and tight tolerancesencountered when a greater zoom ratio is attempted. Turning now to FIGS.6 and 7, a first embodiment of a scope optical train, according to thepresent invention is shown schematically at 130. FIG. 6 shows a scope130 configured for a 1× zoom, while FIG. 7 shows scope 130 configuredfor a 15× zoom. Scope 130 includes objective lens group 132, ocular lensassembly 134, first erector lens assembly 136, second erector lensassembly 138 and third erector lens assembly 140. In this embodimentobjective lens assembly 132 is a triple lens assembly according to atypical known arrangement. An image is projected through lens assembly132 to provide a first intermediate image 142, which is projectedthrough the first erector lens assembly 136 to generate a secondintermediate image 144, which as it is inverted relative to the firstimage 142 is oriented correctly for viewing. Second image 144 is, inturn, projected through second erector assembly 138 to generate a thirdintermediate image 146, which in turn is transmitted through thirderector assembly 140 to generate fourth intermediate image 148. Becauseimage 148 has been inverted twice, relative to the second image 144, itis oriented correctly for viewing by the human eye. The fourth image isthen transmitted through ocular lenses 134 to a viewer using the scope130.

It has been found that some optical artifacts may occur along theoptical train described above. To prevent these artifacts,non-magnifying spheroid or “field” lenses 150 are interposed in theoptical train.

Turning now to FIGS. 8, 9, 10 and 11 which show the optical train ofanother embodiment of a scope 200, in schematic, ray trace form. In thisembodiment the second (central) erector assembly 204 is a roof prismrather than an adjustable, magnifying erector lens assembly as in scope130. First erector assembly 202 projects an inverted image at thelongitudinal middle of prism 204. Third erector assembly receives thisimage and projects an inverted image that ocular lens assembly 208receives and presents to the eye of a user. First erector assembly 202includes a focus or collector lens group 202 a and a zoom lens group 202b. In like manner third erector assembly 206 includes a focus lens group206 a and a zoom lens group 206 b. The focus lens groups 202 a and 206 ado help the zoom, but principally they maintain the focus overmagnification changes and the zoom lens group 202 b and 206 b do helpfocus, but principally they zoom.

FIG. 8 shows the optical train of scope 200 as it is configured at itshighest power 15× magnification setting. FIG. 9 shows the optical trainof scope 200 as it is configured at a 10× power setting. The zoom lensgroup 206 b of third erector assembly 206 has been moved rearward,relative to the configuration shown in FIG. 8.

FIG. 10 shows the optical train of scope 200 as it is configured at a 5×power setting. The zoom lenses 206 b of the third erector assembly 206have been moved back further, and the zoom lens 202 b of the firsterector assembly 202 has also been moved back. FIG. 11 shows the opticaltrain of scope 200 as it is configured at a 1.5× power setting. Both thefocus lens 202 a and the zoom lens 202 b of the first erector assembly202 are moved rearward relative to the configuration of FIG. 10 as arethe zoom lenses 206 b of third erector assembly 206.

FIGS. 12A and 12B show a preferred embodiment of a mechanism 210 forimplementing a moveable lens train similar to that of FIGS. 8-11. Lensmounts 212, 214, 216, and 220 and roof prism 218 are hosted by cam tube230, with each lens mount pin 232 being accommodated by cam tube slot212′, 214′, 216′, 220′ and slots 218′, respectively. Roof Prism 218 hasa roof prism mount that has a pair of pins similar to pins 232, butthese elements are not shown in the drawing, for ease of presentation.Pins 232 fit through their respective slots and into a slot formed inthe top-interior of the central tube housing 17. An actuator permits auser to rotate cam tube 238, thereby moving lens mounts 212 through 220longitudinally, according to a scheme manifested by the cam slots 212′through 220′. The fact that pins 232 are fit into the slot (not shown)in the top-interior of the housing 17, prevents the lenses and prism 212through 222 from rotating as they translate longitudinally. Lens 240 isa fixed, field collector lens. In one preferred embodiment, twoidentical 3× zoom assemblies of well known design are entrained to forma 9× zoom.

FIG. 13A is a side-sectional view of an objective assembly 310 having ahousing 312, that fits into the objective assembly exterior housing 14.Housing 312 can pivot, in exterior housing 14, in order to permitwindage and elevation adjustment, while not breaking a water resistantseal at the front end of scope 10. To achieve this object, assemblyhousing 312 includes a rim having a forwardly inward-sloping surface316, which mates with a ball seat-ring 318 having matching curvature.Accordingly, surface 316 fits into ball seat-ring 318 in such a mannerthat a seal is formed that permits the pivoting of objective assembly310. An O-Ring 320 and a torroid-shaped spring 322 ensure that surface316 is forced into seat-ring 318 with sufficient pressure to maintain agood seal. Objective lens pair 324 and lens 326 focus light in a firstimage plane and have a combined nodal point that is between the two lensgroups. Because the pivot point is far forward, with the front ofhousing 312 rocking in the ball seat ring 318, the pivot point isseparated from the nodal point of the objective assembly 310. If thepivot point were coincident with the nodal point of assembly 310, itwould cause aberrations in the image presented to the viewer. In analternative preferred embodiment, not shown, the objective assembly istranslated transversely, to cause a misalignment of its centerline withthat of the subsequent optical train. With this embodiment the potentialproblem of a coincidence of the nodal point with the pivot point iseliminated, as there is no pivot point. Accordingly the objectiveassembly can be shortened and reduced to a single lens group.

Referring to FIGS. 13A and 13B, windage adjust assembly 18 and anelevation adjust assembly 20 both use a set of rings to adjust windageand elevation. A windage drive ring 352 (FIG. 13C) and an elevationdrive ring 354 both have a uniformly circular outer surface, but avarying thickness, so that an interior surface 355 is displaced from theouter surface by a distance that changes in a uniform manner over a“drive range,” which in one preferred embodiment is a complete rotation.The interior surface contacts a drive pin 356, retained by seal 358,which contacts a side-rear surface of objective assembly 310, so that asthe drive ring 352 or 354 is rotated the pin 356 is either pushedinwardly or permitted to retract, so that the rear of objective assembly310 is pushed to a new position, or permitted to move back to a morecentered orientation, as it is urged to do by torroid spring 322. In apreferred embodiment, rotation of drive rings 352 and 354 is limited toa single rotation, thereby sparing users the task of keeping track ofthe number of rotations that have been introduced during use.

A windage marking ring 362 and an elevation marking ring 364 are engagedabout windage drive ring 352 and elevation drive ring 354, respectively.Additionally, each marking ring 362 and 364 has a prominence 370 that isvisible to a shooter having one eye looking through the scope, so thathe may easily check the windage and elevation settings without takinghis eye off a target. In a preferred embodiment each prominence 370 hasa different appearance when viewed from the rear, so that they can bedistinguished without the need for any depth perception on the part ofthe user. Each marking ring 362 and 364 may be disengaged from its drivering 352 and 354, respectively, by loosening a pair of zero adjust setscrews 372. This permits a user to adjust the relationship betweenwindage and elevation ring position and apparent reticle pointingdirection, to compensate for errors in scope orientation, so that thereticle may be well-aligned with an ideal orientation, such as riflebore-sight plus a slight upward tilt, to permit bullet drop at a nominalrange of perhaps 100 meters. This may be done by placing scope into theideal, desired orientation, disengaging the marking ring 362 or 364 fromthe drive ring 352 or 354, moving the marking ring 362 or 364 to apredetermined zero position and re-engaging the marking ring 362 or 364to its drive ring 352 or 354, respectively. Subsequent apparent reticlemovements are then made relative to the ideal zero position.

Finally, a click ring 374, having a set of circumferentially spacedridges is placed so that it is contacted by one of a pair ofspring-loaded clickers 376. As either marking ring 362 or 364 is turned,a clicker 376 makes a click sound each time it is moved past a ridge onclick ring 374. Shooters may use this to monitor the amount they haveturned ring 362 or 364 without viewing the ring 362 or 364.

Referring to FIGS. 14 and 15, the zoom actuator mechanism 410, includesa shaft 412, having a helical groove 414 formed into it and a gear 415at one end. Shaft 412 is mounted in a small recess 416 and a largerecess 417, which accommodates gear 415. During assembly, after shaft412 has been placed in recesses 416 and 417 a threaded plug 418 isinstalled into the end of the large recess 417, to retain shaft 412.When so mounted gear 415 contacts a set of matching teeth 420 defined onthe surface of cam tube 238, through an opening (not shown) in the largerecess 417.

Shaft 412 is threaded through an aperture 428 in a slider 430, which isseated in a groove 432 formed in the exterior of scope housing 12. A peg434 is mounted in slider 430 and engages groove 414, so that as slider430 is moved along groove 432, shaft 412 is rotated. In turn gear 415turns cam tube 238 by way of teeth 420. In a preferred embodiment slider430 has a range of motion of greater than 2 cm.

Referring to FIG. 18, in an alternative preferred embodiment the zoomadjustment takes the form of a knob 620 at the ocular end of the scope,driving cam tube 238 by means of a bevel gear 630. Referring to FIG. 17,this embodiment is adapted for use mounted on a rifle 612, by way of ascope mount having a rear mounting ring 614 and a front mounting ring616. FIG. 17, also shows an elevation adjust knob 640, which performsthe same function in similar manner to elevation adjust ring mechanism20, with rotation pushing an element against assembly 310. Because ofthe far forward placement of knob 640, the scope may be installed in afar forward position, giving greater eye relief, without a concern ofhaving conflict between a windage and elevation knob tower and the frontmounting ring 616, as has heretofore been the case. Skilled persons willappreciate that this placement would be also possible with windage andelevation adjust ring mechanisms 18 and 20. The two mounting ringconfiguration is typically used by hunters and other recreationalshooters. The zoom actuator mechanism 410 is designed to be used withmilitary rifles, which are mounted without the use of mounting rings.

In either the slider or knob embodiment, the zoom actuation schemepermits cam tube 238 to be rotated by greater than a single fullrotation. This permits the design of cam tubes having slots in the shapeof irregular helices that wrap about the cam tube 238 by more than acomplete rotation. This permits an additional freedom of design,potentially permitting a greater range of erector lens movement.

Referring to FIGS. 14, 15, 16A and 16B the focus mechanism 510 of thescope 10, includes a focus-adjustment roller 512, which is partiallyprotected by roller housing 513. Also, roller 512 is rigidly attached toa drive gear 514, which in turn drives a focus cam tube 516 having teethmatching those of drive gear 514. Tube 516 also defines a cam-tube slot518. A focus lens assembly 520 includes a cam-slot follower pin 522, sothat as cam tube 516 rotates, lens assembly 520 is moved either forwardor back, thereby changing the focus of scope 512. A coil spring 540(FIG. 16A) urges pin 522 to contact the rear of slot 518, therebypreventing potential slop in the position of lens assembly 520 caused byslight room for forward and backward movement of pin 522 in slot 518.Skilled persons will recognize that the cam-tube slot 518 can bedesigned so as to create a desired focus profile, so that it is possibleto finely adjust the focus, even at a long range. In one preferredembodiment a linear relationship is created between rotation of roller512 and focus range, with possible ratios being one complete rotationfor every 50, 75 or 100 meters, from a range of 10 meters to a range of400 meters or more. With a relationship like one of these, at any rangea small tweak to focus roller 512 will provide a fine adjustment to thefocus range.

In one preferred embodiment a first focus roller assembly, having arelatively large diameter drive gear. for speedy, gross adjustments ofthe focus, and a second focus roller assembly is provided, displacedaround the body of the scope from the first focus roller assembly, witha relatively small diameter drive gear for fine adjustment of the focus.

A scope constructed in accordance with the preceding disclosure, has anumber of advantages relative to current scope design. First, such adesign will tend to be far easier to manufacture, resulting in a lowerdefect rate and ultimately less expense. First, a high zoom ratio scopebuilt with currently available methods drives very tight tolerances inboth the lenses used and the cam tube slots. This is because many of thelenses are used quite differently over different portions of the zoomrange, so that at a first zoom position, for example, the lens curvaturenear the center of the lens may be absolutely critical, whereas at asecond zoom position the curvature towards the exterior becomescritically important. Accordingly the shape of the lens must be veryclose to the ideal lens shape specified. The tighter the tolerance, theharder it is to meet the requirement in lens manufacturing and the moretime and effort must be spent after each lens is manufactured, ensuringthat it meets its tolerances. Also, the range of lens movement is muchgreater in previous designs for high zoom-ratio scopes, and with similarrationale to the need for tight lens tolerances, the cam tube slots mustbe machined with exacting precision.

Fortunately, because the windage and elevation adjustment mechanisms 18and 20 alter the position of the objective assembly instead of a camtube, as in most previous scopes, the cam tube 238 may be made with alarger diameter, permitting a thicker circumferential wall. Athicker-walled cam tube is easier to accurately machine, and is alsoable to withstand the shock of recoil better than a thinner-walled camtube. Whereas currently available designs may have a wall-thickness ofas little as 0.65 mm. The cam tube 238 of scope 10 has, in a preferredembodiment, a circumferential wall-thickness of 1 mm, 1.5 mm or greater.In a preferred embodiment a similar wall thickness is used in focus camtube 516. In one preferred embodiment scope 10 is made with sufficientwall thicknesses for tubes 238 and 516 that it can be used with a 0.50(inch) caliber rifle. In the prior art, this has typically not beenachievable because of the powerful recoil of this type of rifle.

Moreover, a design using two erector lens assemblies permits a reductionin the amount of curvature in the cam tube slots making it possible touse cam tube slot followers (pins 232, FIGS. 12A and 12B) that have agreater length than would otherwise be possible. In one preferredembodiment of scope 10, pines 232 are replaced with elliptical slotfollowers that are 7 mm long. Longer slot followers have greaterdurability because they spread the force of the rifle recoil over alarger area of the slot follower.

Additionally, windage and elevation adjustment assemblies 18 and 20permit a shooter to check, and even modify, the windage and elevationadjustment without removing his aiming eye from the scope. The greatersize of marking rings 362 and 364 in comparison with currently availableknobs, makes them relatively easy to manipulate. Moreover, in apreferred embodiment it is only possible to turn the windage andelevation marking rings 362 and 364 by less than a full rotation,thereby avoiding the problem of ambiguity in reading the windage andelevation adjustments that systems that permit more than a full rotationtypically incur.

Military rifles are typically light enough (less than 4 kg) to besupported by the same hand that is pressing the trigger, leaving theother hand (the left hand for a right handed shooter) free. Also, ascope is attached to a military rifle without mounting rings, leavingmore of the side of the scope accessible. Zoom actuator assembly 22 islocated so that when scope 10 is attached to a military rifle, a shootermay adjust the zoom with his free left hand (for a right handed person).An alternative preferred embodiment is optimized for left handedsoldiers, and has the actuator assembly located on the opposite side ofthe scope from the way it is shown in the drawings. In addition, therelatively lengthy slider range provides a good accuracy and precisionof adjustment.

The embodiment shown in FIG. 18, wherein a knob 530 is positioned on theocular portion of the scope, is optimized for hunters and otherrecreational shooters. As a hunter's scope is typically attached to therifle with mounting rings, having a slider assembly 22 could proveimpractical. Accordingly, a knob is provided on the right side of thescope, so that a right-handed shooter can easily use his right hand toreach up and adjust the knob. An alternative preferred embodiment isoptimized for use by a left-handed shooter and has the knob positionedon the left-hand side of the scope. Either the slider or the knobembodiment, however, permit the cam tube to be rotated by a full 360°,as opposed to a typical scope, in which the cam tube can only be rotatedby a mere 180°. The greater rotation lens movement to be performed overa greater rotational distance, easing design constraints.

The design of the focus assembly permits a focal profile that isoptimized for the particular scope. For some scopes the far range focusmay be very important, and it is advantageous to shape the focus camslot so that a movement of the focus roller 512 translates in an optimalmanner to focus adjustment. Also, the location of the focus roller 512on the left hand side of the scope, from the perspective of a shooter,permits a military rifle shooter to adjust the focus with his free lefthand, just as with the zoom actuator assembly 22. In all, the windageand elevation, the focus and the zoom, can all be adjusted by the userof a military rifle, with his free left hand.

While a number of exemplary aspects and embodiments have been discussedabove, those possessed of skill in the art will recognize certainmodifications, permutations, additions and sub-combinations thereof. Itis therefore intended that the following appended claims and claimshereafter introduced are interpreted to include all such modifications,permutations, additions and sub-combinations as are within their truespirit and scope.

The invention claimed is:
 1. A method of focusing a rifle scope, by a right-handed shooter, on a scene of interest: (a) providing a rifle assembly including a scope mounted on a rifle having a stock, said scope having a left-hand side, from said shooter's perspective; (b) wherein said scope has a focus roller, mounted on said left-hand side of said scope; (c) placing a left hand on said stock, and holding said stock with said left hand, so that the left-hand thumb can reach said focus roller; and (d) moving said focus roller with said left-hand thumb until said scene of interest is in focus.
 2. The method of claim 1 wherein said focus roller has an axis of rotation substantially parallel to a longitudinal dimension of said scope, and is displaced to the left and downwardly from the transverse center of said scope.
 3. The method of claim 1, further including, looking through said scope while performing steps b, c and d. 